Gas cell



w.. G. Gow

Aug. 29,A 1939.

GAS CELL Filed June 17, 1937 FIG.2b.

FIG. 2a.

INVENTOR WILLIAM GEORGE GOW ATTORNEY in commercial quantities, will beof uniform conf Patented Aug. 29, 1939 UNITED STATES PATENT OFFICE GSCELL Maplewood, N, J.

Application June 17, 1937, Serial No. 148,65 7

3 Claims.

This invention relates to a novel gas cell for use in apparatus toanalyze gases by the thermal conductivity method which, whenmanufactured stants of performance.

Previously, the general practice in designing gas cells for anlyzinggases by the thermal conductivity method has been to provide anelongated cell' with a straight lament fixed therein held in position bytension means. In this type of cell the space which is lled with gas isrelatively large, the filament is subject to distortion,

the path of the gas -through the cell is relatively long. Although thistype of cell may be satisfactory for laboratory work, theabove-mentioned features comprise serious disadvantages both inoperation in a commercial analyzer such as that described in my PatentNo. 2,080,660 and in uniform manufacture in commercial quantities. In myabove-mentioned patent I have shown a gas cell which overcomes some ofthese disadvantages. Instead of using a long piece of straight wire, Ihave used a short, spiral filament which is held in the gas cell bylead-in wires thus reducing the length of the path of the gas throughthe cell. There remain; however, many difficulties in the manufacture ofthis type of cell. Prominent among these are the dimculties of properlypositioning the filament with relation to the bottom of the cell,properly positioning the filament with respect to the side wallsrof thecell, keeping the lead-in wires from touching each other or the sidewalls of the cell, preventing the distortion of the lead-in wires duringthe baking of the cement used to seal them in the cell.

A further difliculty is encountered in manufacturing this type of cell.If only a small amount of cement is used, a large air space is leftabove the active filament, this must be filled with gas and then clearedout for each test. This considerably' slows the speed of operationbecause of the time required to clear the gas out of the dead spaceabove the filament. I have found that it is impractical to try to llthis dead space with cement, 'because in .doing so th'e excess amount ofcement used will run to the bottom of the cell or adhere to the lamentsometimes completely covering the filament.

Bymy present invention I have overcome these disadvantages and provideda gas cell which is very compact, accurate and emcient and-easy tomanufacture uniformly in commercial quantities. A better understandingof my invention may be had by reference to the accompanying draw- (cl.'z3-51j ing in which Fig. 1 is a cross-sectional view through the centerof the kind of gas cell in former use and Figs. 2a and 2b arecross-sectional views on different axes through the center of myimproved gas cell.

' Referring to Fig. 1, the gas cell formerly used consists of a casing3, the upper part of which is formed as a bolt-head 4, so that it may bereadily seized in order to turn it into position in the cell block.Below this bolt-head the cell is, for a portion of its length, threadedasis shown at 5, so that it may be screwed into the cell block. 'I'helower portion of the cell is of a reduced diameter as shown at 6. Nearthe bottom of the cell two or more holes, l, 1, are bored to permit thegas to be analyzed or the 4standard gas, as the case may be, to enterthe cell and surround the filament 8.

The filament 8 is located in a cylindrical opening 9, extending to thebottom wall I2 of ,the cell and is firmly attached to lead-in wires I0,I0. These lead-in wires enter through an opening at the top of the celland after being properly positioned are, for a portion of their length,surrounded by cement I I which then must be baked to hold the lament inthe proper position.

It is obvious in the manufacture of such a cell that it is verydifficult to hold the lead-in wires in proper position while insertingthe cement II so that the filament 8 in every case will be the samedistance from the bottom I2 of the cell. It is also difficult to holdthese lead-in wires so that the axis of the filament B will remainparallel to the bottom I2 of the cell and to keep the lateral spacing ofthe filament 8 from the side walls 6 the same in every case. Variationsin these distances will seriously affect the conductive characteristicsof the cell and will thus prevent the useof two cells, one for thestandard gas and one for the gas to be analyzed, in the same cell blockunless careful choice from anumber of cells is made to get two cellswhich perform as a pair, that is, which have spacings which do not vary.

A further difficulty arises when the cement II is dried out by a heatprocess. Gas or air bubbles formed during this baking cause distortionin the lead-in wires I0, I0 which will change the position of thefilament 8. Thisdistortion will affect the spacing. of the filamentrelative to the cell Walls with the detrimental results noted above. Thedistortion in the lead-in wires caused by this heating is in many casessuihcient to cause a short circuit either by adjacent turns in thespiral filament touching or by the lead-in wires o which has an enlargedportion resting against a shoulder in the gas cell and thus positioningthe filament accurately.

Referring to Fig. 2a, the cylindrical opening 9 in the cell has at thetop an enlarged portion 9a.

The lead-in wires before being placed in the cell are sealed in a glassspacing member I3 having a butt portion I8.4 The lead-in wires aresealed in this glass butt. Since this process is visible, the distanceof the filament from the end of the 24) butt I8 caureadily be determinedso thatr the position of the iilament 8 with relation to the butt I8 canbe easily and accurately made alike in different cells. The spacingmember I 3 hasy an ,enlarged portion i3d. The diameter of this portionI3a is too great for it to go below the.

shoulder 9b terminating the enlarged portion 9a of the cell. Therefore,the position of the iliament 8 with relation to the bottom I2 of thecell and also with relation to the side walls is accurately deiined byrst mounting it in the the butt I8, the spacing member I 3 is placed inthe cell so that the enlarged portion Ida, thereof rests against theshoulder 9b in the gas cell, then cement I i is placed in the cell tohold the spacing member I3 tightly in place. The diameter of theenlarged portion I3a of the spacing member is a little less than thediameter of the enlarged portion 9a of the casing and cement Ii lls thissmall annular space. If desired, the inside of the spacing member 'I3'may be completely filledl with cement. v

It is to be noted that the open space into which the gases ow can bemade much smaller in this type of cell than in that described 'inFig. 1. This increases the eiiiciency of the cell and the o speed withwhich a gas sample may be cleared out for a subsequent reading on adifferent sample.

While I havementioned above a glass spacing Y member I3, it is to beunderstood that this may 6o sleeve which may be of any ceramicinsulating material has two longitudinal openings I5, I5 through whichthe lead-in wires I0, I0 pass. This prevents any possibility of thelead-in wires coming in contact with each other, and permits 05 the useof a non-insulating cement.

I have also found it of advantage to use an insulating ceramic sleeve I6surrounding the filament. This is loosely placed in the opening 9 beforethe spacing member I3 is tted therein.

The sleeve I6 has two slots or more or holes Iland when placed in thecell the sleeve I6 is rotated so that the slots I I register with theopenings 1 so that the gas to be analyzed can surround the ilament 8.

If desired, the thickness of the sleeve I6 may be made suflicientlygreat so that the top thereof will form a shoulder against which anenlarged portion of the spacing member I3 may rest and the spacingmember may be positioned by this mean's instead of by resting againstthe shoulder 9b in the wall of the cell. However, in a, small size cellit is undesirable to use the space required for making the sleeve I6 ofsuiiicient thickness for this `purpose and4 I prefer to position thespacing member I3 as shown in Fig. 2a except in larger sized cells.

While a preferred embodiment of the present invention has beenhereinbefore described, it will be readily apparent that many andvarious changes and modifications in form, structure and arrangement ofthe parts may be made without departing from the spirit oi the inventionand it will be understood that all and any such changes and modicationsare contemplated as a part of this invention as deiined in the appendedclaims.

What I claim is:

l. A cell for analyzing gases by the heat conductivity method comprisinga shell having an internal openingy for substantially its entire length,said internal opening having an enlarged portion andl a narrow portionforming a substantially square shoulder therebetween, an insulatingspacing member disposed therein having .anV enlarged portion, a narrowportion and a butt portion, said enlarged portion being of too greatdiameter to fit Within the narrow portion of the opening in the cell, aspiral ilament connected to lead-in wires passing through saidinsulating spacing member and firmly attached to the butt portionthereof by reason of which the position of the filament relative to thewalls of thecell is determined and said filament is held away from andbelow said butt portion and means for sealing said insulating spacingmember and lead-in wires in said shell all forming a' unitary sealedstructure.

2. A cell for analyzing .gases by the heat conductivity methodcomprising a shell, an insulating spacing member held in a fixedposition there- -in by an internal abutment in said shell, a resistancelament iirmly attached to but spaced away from said insulating spacingmember by lead-in wires and an insulating sleeve surrounding saidiilament but-spaced therefrom to prevent it touching the walls of saidshell and a seal for holding said spacing member in position.

, 3. A cell for analyzing gases by the heat conductivity methodcomprising a shell, a hollow insulatingy spacing member held in a iixedposition therein by an internal abutment in said shell, a resistancefilament iirmly attached to said insulating spacing member by lead-inwires, said lead-in wires passing through the end of said insulatingspacing member, an insulating sleeve within said insulating spacingmember having channelsthrough which said lead-in wires pass and aninsulating sleeve surrounding `said iilament to prevent it touching thewalls of said shell and a seal for holding said spacing member inposition.

- WILLIAM GEORGE GOW..

